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    <title>Document</title>
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    <p>中国</p>
    <p>武汉</p>
    <p class="jia">加油</p>
    <p id="wan">祖国万岁</p>
    <h3 class="jia">祖国万岁</h3>

    <script>
       $("p").css("color","red");  //标签选择器，获得所有p
       $(".jia").css("color","red"); //类选择器
       $("#wan").css("color","red"); //ID选择器,具有唯一性
       $(".jia,#wan").css("color","red"); //并集选择器， .jia和#wan
       $("h3.jia").css("color","red"); //交集选择器,既是h3标签,又拥有.jia的元素

    </script>
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